Your "next;" makes it skip the rest of the while loop body. Your if has the same thing in both branches?? How about something like this (in the cb, the requirement to remove the ; was revealed):

my $prev;
while (my $line = <>) {
    chomp $line;
    print $prev, "\n" if defined $prev && $line !~ s/^;/$prev/;
    $prev = $line;
}
print $prev, "\n" if defined $prev;
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