in reply to regular expression problem

Here is one solution:

$string =~ s/$regex/eval "\"$replace\""/e;

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The problem with your method was that to get that to work it would have to do variable substitution twice, first to substitute $replace with '$2 $1', then a second variable substitution of $2 and $1. Using eval in connection with the e modifier basically does just this second variable substitution.

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Re^2: regular expression problem
by johngg (Canon) on Aug 17, 2009 at 12:44 UTC

    Rather than use eval inside the replacement term you can use a double ee modifier (see the s operator in Regexp Quote Like Operators).

    $ perl -le '
> $str =  q{10 09};
> $reg =  q{(\d+) (\d+)};
> $rep =  q{"$2 $1"};
> $str =~ s/$reg/$rep/ee;
> print $str;'
09 10
$

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    I hope this is of interest.

    Cheers,

    JohnGG

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Re^2: regular expression problem
by perl_fan (Novice) on Aug 17, 2009 at 12:13 UTC 
    Super cool

Thanks you are a Hero
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