Golfscript, 8 chars

This defines a function called A

{$\$=}:A 

Test cases

; 'boat' 'boat' A 'toab' 'boat' A 'oabt' 'toab' A 'a' 'aa' A 'zzz' 'zzzzzzzz' A 'zyyyzzzz' 'yyzzzzzy' A 'sleepy' 'pyels' A 'p' 'p' A 

Golfscript, 8 bytes

This defines a function called A

{$\$=}:A 

Test cases

; 'boat' 'boat' A 'toab' 'boat' A 'oabt' 'toab' A 'a' 'aa' A 'zzz' 'zzzzzzzz' A 'zyyyzzzz' 'yyzzzzzy' A 'sleepy' 'pyels' A 'p' 'p' A 

Golfscript - 8 chars

This defines a function called A

{$\$=}:A 

Test cases

; 'boat' 'boat' A 'toab' 'boat' A 'oabt' 'toab' A 'a' 'aa' A 'zzz' 'zzzzzzzz' A 'zyyyzzzz' 'yyzzzzzy' A 'sleepy' 'pyels' A 'p' 'p' A 

Golfscript, 8 chars

This defines a function called A

{$\$=}:A 

Test cases

; 'boat' 'boat' A 'toab' 'boat' A 'oabt' 'toab' A 'a' 'aa' A 'zzz' 'zzzzzzzz' A 'zyyyzzzz' 'yyzzzzzy' A 'sleepy' 'pyels' A 'p' 'p' A