I see no reason to

• first read in the whole file and then process it line by line
• doing a similar tes ttwice, when one will do

I'd just do

while(<FH>) {
    push @required, $_ if /^abcde.*partname$/;
}
[download]

or, if that's all you do with those lines:

while(<FH>) {
    print C if /^abcde.*partname$/;
}
[download]