$line =~ s/$line/$prefix: $line/;
Ooops. You're treating the contents of $line as a regex on the left side of a substitute. Many of those lines have regex-significant characters, so they don't match themselves.

You can do this the hard way: 

$line =~ s/\Q$line/$prefix: $line/;

[download]
Or the much easier way: 
$line =~ s/^/$prefix: /;

[download]

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

In reply to •Re: concatenation through substitution? by merlyn
in thread concatenation through substitution? by Anonymous Monk

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