Perl 5, 27 32 22 bytes

{{open my$h,'>o'}redo} 

If simply changing the modification timestamp of a file suffices...

Quick explanation:

{ # Braces implicitly create/mark a loop. { # New, more localized scope, for `my` variable. open my $filehandle, '>', 'o'; # Writing to file "o". # close $filehandle; # Called implicitly when # variable gets destroyed. } # Scope gets destroyed; so does $filehandle. redo; # ...the loop. } 

Previous solution (32 bytes): {{open my$h,'>o';print$h 1}redo}

Edit: {open F,'O';print F 1;redo} ← Didn't test the code before posting; now I had to correct it.

Perl 5, 27 32 22 bytes

{{open my$h,'>o'}redo} 

If simply changing the modification timestamp of a file suffices...

Quick explanation:

{ # Braces implicitly create/mark a loop. { # They also create closures, for `my` variables. open my $filehandle, '>', 'o'; # Writing to file "o". # close $filehandle; # Called implicitly when # variable gets destroyed. } # $filehandle gets destroyed because there are no references to it. redo; # ...the loop. } 

Previous solution (32 bytes): {{open my$h,'>o';print$h 1}redo}

Edit: {open F,'O';print F 1;redo} ← Didn't test the code before posting; now I had to correct it.

Perl 5, 27 32 bytes

{{open my$h,'>o';print$h 1}redo} 

Quick explanation:

{  # <-- Braces implicitly create/mark a loop. {  # <-- New, more localized scope, for `my` variable. open my $filehandle, '>', 'o';  # Writing to file "o". print $filehandle 1; # Yes, no comma there!  # Search "Indirect Object Notation". close $filehandle;  # Called automatically when the # variable gets deleted. }  # <-- Scope gets destroyed. redo;  #...the loop! } 

Edit: {open F,'O';print F 1;redo} ← Didn't test the code before posting; now I had to correct it.

Perl 5, 27 32 22 bytes

{{open my$h,'>o'}redo} 

If simply changing the modification timestamp of a file suffices...

Quick explanation:

{ # Braces implicitly create/mark a loop. { # New, more localized scope, for `my` variable. open my $filehandle, '>', 'o'; # Writing to file "o". # close $filehandle; # Called implicitly when   # variable gets destroyed. } # Scope gets destroyed; so does $filehandle. redo; # ...the loop. } 

Previous solution (32 bytes): {{open my$h,'>o';print$h 1}redo}

Edit: {open F,'O';print F 1;redo} ← Didn't test the code before posting; now I had to correct it.

Perl, 27 bytes

{open F,'O';print F 1;redo} 

Expanded version:

{ # <-- Braces implicitly create a loop. open FILEHANDLE, 'O'; print FILEHANDLE 1; redo; # Redo the loop code. } 

Perl 5, 27 32 bytes

{{open my$h,'>o';print$h 1}redo} 

Quick explanation:

{ # <-- Braces implicitly create/mark a loop. { # <-- New, more localized scope, for `my` variable.   open my $filehandle, '>', 'o'; # Writing to file "o".   print $filehandle 1; # Yes, no comma there!   # Search "Indirect Object Notation". close $filehandle; # Called automatically when the    # variable gets deleted.  } # <-- Scope gets destroyed.  redo; #...the loop! } 

Edit: {open F,'O';print F 1;redo} ← Didn't test the code before posting; now I had to correct it.