(not $condition or $a =~ s/foo/bar/) and print $a;

(not $condition or $a =~ s/foo/bar/) and print $a;

#!/usr/bin/perl
# vim: set ts=4 sw=4 et sta:
use strict;
use warnings;

my ( $cond, $aa );

for $cond ( 0 .. 1  ) {

    $aa = 'fix';
    ( not $cond or $aa =~ s/foo/bar/ ) and print "$cond: $aa\n";

}

$ perl -wle'                
$condition = 1;
$a = "foo";
print $condition ? ($a=~s/foo/bar/, $a) : $a;'
1bar

(not $condition or $a =~ s/foo/bar/ or 1) and print $a;