I think part of your problem is that you are using square brackets [] inappropriately. They set up a character class so your [.]+ will match one or more literal full-stops; in a character class the full-stop loses it's meta-character meaning of matching any character and becomes a literal. Doing [abc]{3} would match exactly three of either a or b or c.

It also makes things easier when matching paths to choose a delimiter character other than "/" by using the m operator. You can choose a character like the pipe symbol "|" or balanced brackets like {}. Once you've done that you no longer have to escape the "/" characters.

My (non-tested) attempt at your sub die_clean would be:-

sub die_clean
{
    my $input = shift;
    my ($msg, $line) = $input =~ m{(.+?)( at /\S+ line \d+\.$};
}
[download]

The $ sign anchors the match to the end of the string just on the off-chance that the "MY ERROR" part contains "at /pathe/to/file line n." which is unlikely but stranger things have happened. The .+? says match one or more of any character in a non-greedy fashion. You want to do this otherwise a .+ without the ? would consume the entire string and not leave any characters for the rest of the regular expression to match.

Cheers,

JohnGG