almaric has asked for the wisdom of the Perl Monks concerning the following question:

I have 
$a="a    ";

foreach (1..(length $a)) {
  print "a(".$1.")(".$2.")\n" if ( $a =~ m/^a( {$_})( )/ ) ;
}

[download]
This prints 
a( )( )
a(  )( )
a(   )( )

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Does anyone know a way to write a single regexp ($regexp) that results in the same output when inserted into the following code? 
$a="a    ";

while ( $a =~ m/$regexp/ ) {     # or m//g, m//gc, ...
  print "a(".$1.")(".$2.")\n";
}

[download]
Thanks for any help

regards,
almaric

Replies are listed 'Best First'.
Re: With one regexp
by BrowserUk (Patriarch) on Feb 29, 2004 at 12:49 UTC

    Something like this?

    $s ='a123456789';
$p = 0; 
print "a($1)($2)\n" while ++$p and $s =~ m[^a(.{$p})(.)];

a(1)(2)
a(12)(3)
a(123)(4)
a(1234)(5)
a(12345)(6)
a(123456)(7)
a(1234567)(8)
a(12345678)(9)

    [download]

    I put numbers in so I could see what was going on, but it works fine with spaces too.

    $s ='a       ';
$p = 0; print "a($1)($2)" while ++$p and $s =~ m[^a( {$p})( )];

a( )( )
a(  )( )
a(   )( )
a(    )( )
a(     )( )
a(      )( )

    [download]

    Update: Or if you like cute, you can do away with the external loop and use backtracking. 

    $s ='a       ';
$s =~ m[^a(.+?)(.)(?{ print "a($1)($2)" })(?!)];

a( )( )
a(  )( )
a(   )( )
a(    )( )
a(     )( )
a(      )( )

    [download]
    Examine what is said, not who speaks.
    "Efficiency is intelligent laziness." -David Dunham
    "Think for yourself!" - Abigail
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