You seem to already know the tool that can help you: regular expressions. Here's what I tried and got exactly the same output for the given input (i.e. same @mail, @text, and File::Copy::copy called with the same parameters as in your code): 
    if (my ($dt, $msg, $source, $destination)
        = $text =~ /([0-9]{4}-[0-9]{2}-[0-9]{2}[ ][0-9]{2}:[0-9]{2}:[0
+-9]{2})
                    [ ]FATAL:[ ]Error[ ]while[ ]copying[ ]
                    (.+)
                    [ ]from[ ]
                    (.+)
                    [ ]to[ ]
                    (.+),
                   /x
        ) {
        ( my $source_without_drive = $source ) =~ s/^\w://;
        my $sourcebis = '\\\\ENCNRW0010' . $source_without_drive;
        File::Copy::copy $source.$msg, $destination;
        push @mail, "$dt $msg from $sourcebis to $destination\n";
        $text =~ s/FATAL: Error while copying /FATAL (Fixed): Error wh
+ile copying /g;
        push @text, $text."\n";
    }
}

[download]

UPDATE: fixed for paths containing spaces.

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

[download]

In reply to Re: Alternatives for index() ... substr() ? by choroba
in thread Alternatives for index() ... substr() ? by zarath

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