UPdate: again, to late :(

without knowing the rest off the code, ussumtions have to be made, but my guess:

if $args{DOUBLE_BYTE} contains a 'y' character (case doesn't matter), $tempport is set to the constant value DB_CATPORT.
Otherwise, $tempport is set to the constant SB_CATPORT.

the following code does the same:

my $tempport;
if ( $args{DOUBLE_BYTE} =~ /y/i ) {
    $tempport = DB_CATPORT
}
else {
    $tempport = SB_CATPORT
}
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