my ($first, $last ) = /(.+",)(.+)/;
$last =~ s//"\n$first"/g;
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I second hdb's reply in general.

Let me add that the
    $last =~ s//"\n$first"/g;
statement from the posted code quoted above is very unlikely to do what you want: it will match the  // null regex pattern globally and do a substitution against what is matched. If there has been a previous successful regex match (e.g., the match in the preceding line), the  // regex matches using the previously matched regex. (If there has been no previous successful regex match, the  // regex matches anything!) As it stands, this substitution seems to be a no-op. If it is part of some carefully thought out strategy, I advise you to abandon it immediately: it has 'maintenance nightmare' written all over it! (In the code example below,  \x22 stands in for an unbalanced  " (double-quote) character.)

>perl -wMstrict -le
"$_ = qq{\"ABC\",\"DEF\",\"This is a test\",\"Hello\"};
 ;;
 my ($first, $last ) = /(.+\x22,)(.+)/;
 print qq{'$last'};
 ;;
 $last =~ s//\"\n$first\"/g;
 print qq{'$last'};
"
'"Hello"'
'"Hello"'
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