How to have Perl repeat the entire sentence with each variable

Question

Consider:

#! /usr/bin/perl @no = (1 .. 20000); foreach(@no) { print "<div id=\"world@no\" onclick=\"javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()\">&nbsp;</div>\n"; }

This is my Perl script, but how do I get it to rewrite the sentence with a new variable each time?

I.e., how do I get it to output the following?

<div id="world1" onclick="javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()">&nbsp;</div> . . . <div id="world20000" onclick="javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()">&nbsp;</div>

Note: Not to be confused with How can I repeat a string N times in Perl? (the search engines can't tell the difference). — Peter Mortensen
– Peter Mortensen, Commented Aug 23, 2023 at 19:53

ysth · Accepted Answer · 2011-07-21 09:34:53Z

Your main problem is interpolating the whole array into your string instead of the loop variable ($_ in your case since you didn't specify one, but I prefer to give it a name).

You can avoid needing to escape the "s by using a different delimiter for your string:

use strict; use warnings; for my $world_no (1..20000) { print qq!<div id="world$world_no" onclick="showDiv_postscreen(); hideDiv_welcomebuttons()">&nbsp;</div>\n!; }

Also, the "javascript:" is only necessary for things like <a href="..."> where a url is expected and you want to supply javascript code instead. It's not needed for onclick, certainly not twice.

At least one answer makes like easier. We need those backslashes so don't waste them. :)

Alexandr Ciornii · Accepted Answer · 2011-07-21 09:29:21Z

1

#!/usr/bin/perl my @no = (1 .. 20000); foreach my $i (@no) { print "<div id=\"world$i\" onclick=\"javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()\">&nbsp;</div>\n"; }

answered Jul 21, 2011 at 9:29

Alexandr Ciornii

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8 Comments

Dimitar Petrov Over a year ago

Why not just use: foreach my $i (1 .. 20_000), otherwise you are loosing memory to prelocate the array size

TLP Over a year ago

@Dimi Or for (my $i = 1; $i <= 20_000; $i++) to avoid loading any memory. ;) Or a while loop, like in my answer.

Alexandr Ciornii Over a year ago

This is the example, in real program array may be created some other way, not every number.

Dimitar Petrov Over a year ago

@TLP: That's also a solution, however I just dont like that syntax ;) Alexandr: My point was that you don't need to create the array at all, because you allocate memory for 20_000 elements.

ysth Over a year ago

TLP: for(;;) doesn't save any memory over for(..)

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cppcoder · Accepted Answer · 2011-07-21 09:32:48Z

#! /usr/bin/perl @no = (1 .. 20); foreach $x (@no) { print "<div id=\"world$x\" onclick=\"javascript:showDiv_postscreen()\;javascript:hideDiv_welcomebuttons()\">&nbsp;</div>\n"; }

user554546 · Accepted Answer · 2011-07-21 09:28:46Z

The @ in the print statement is confusing the interpreter. Also, it isn't what you want, since print "@no" would print out the same thing as join(' ',@no). Instead, you want to interpolate each element of @no into the string that's printed out:

#! /usr/bin/perl use strict; use warnings; #Always use these! my @no = (1 .. 20000); foreach(@no) { print "<div id=\"world" . $_ . "\" onclick=\"javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()\">&nbsp;</div>\n"; }

TLP · Accepted Answer · 2011-07-21 10:12:15Z

I would consider using a variable to count, instead of defining a range. It may feel less intuitive, but it is not.

Also, instead of escaping the double quotes (\"), you can use qq(), which is equivalent.

my $i = 1; print qq(<div id="world$i" onclick="javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()">&nbsp;</div>\n) while ($i++ <= 20_000);

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