if ( $content =~ /\t/ ) {
    $content =~ s/\t//g;
}
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Why are you testing for /\t/ first?    If the substitution operator doesn't find a "\t" it will not remove anything so the first test is superfluous.    And would probably would be better to use the tr/// operator anyway:

$content =~ tr/\t//d;
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    if ( $line =~ /CONTACT/ ) {
        $line =~ s/CONTACT//;
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Why are you testing for /CONTACT/ first?    Just use the substitution operator in the test:

    if ( $line =~ s/CONTACT// ) {
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                if ( $line =~ /(.+?)=.+/ ) {
                    unless ( $cols{$1} and $cols{$1} == 1 ) {
                        $cols{ ucfirst lc $1 } = 1;
                        push @cols, ucfirst lc $1;
                    }
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You are testing for an unmodified $1 but you are storing a modified $1 in the hash so how is the test supposed to work correctly?    And why the two tests on $cols{$1} when the value can only ever be either 1 or undef?

        if ( $$row{$_} ) {
            push @rows, $$row{$_};
        }
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$$row{$_} is usually written as $row->{$_}.