$str =~ s{$pattern}{push @positions, pos $str; $substitution}eg

I never worked with pos so I don't know if that helps you.

It is nearly perfect, but

$wFound = $szText =~ s/$szSearchText/push @wPos, pos $szText;$szReplac
+eText/eg;

foreach my $Line (@wLines) {
    $wLine = Convert::posToLine($szText, $Line);
    if ($wLines[-1] != $wLine) {
        push @wLines, $wLine;
    }
    print "Line: $wLine\n";
}
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doesn't replace correct if the replacement is something like "\L$1\E".

There are two possible workarounds:

A string eval, e.g.

my $subst = 'lc $1';
# and later
$str =~ s{$pattern}{push @pos, pos $str; eval $subst; }eg
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The other one moves the push to the regex:

use strict;
use warnings;
use Data::Dumper;

my @pos;
my $str = "foobarbaz";

if ($str =~ s{([aeiou]+)(?{ push @pos, pos $str })}{<--$1-->}g){
    print Dumper \@pos;
    print $str, "\n";
}
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But please read the notes in perlre on the (?{...}) construct.

---

Perl 6 in German -- Difficult Sudoku

One possibility is to step through substrings of the file content, starting at each new line. Here is a sketch:

my $content = do { local $/; <DATA> };

my ( $ln, $start) = ( 1, 0);

while ( $start < length $content ) {
    if ( substr( $content, $start) =~ s/.../.../ ) {
        print "line $ln changed\n";
    }
    $start = 1 + index( $content, "\n", $start);
    ++ $ln;
}
__DATA__
aaa
bbb
ccc
ddd
eee
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