Perhaps you could read all of the lines from your second file, before starting to process the first, and construct a single regular expression with all of the strings you want to exclude.
johngg@shiraz:~/perl/utils$ perl -Mstrict -Mwarnings -E '
open my $file2FH, q{<}, \ <<__EOD2__ or die $!;
/dumpx/DUMP4X/var/level6/55
/dumpx/DUMP4X/var/level7/58
__EOD2__
my $rxExcl = do {
chomp( my @lines = <$file2FH> );
local $" = q{|};
qr{@lines};
};
close $file2FH or die $!;
open my $file1FH, q{<}, \ <<__EOD1__ or die $!;
/dev/sda3 6 Fri Apr 12 04:27:19 2019 +0100 /dumpx/DUMP3X/var/level6/
+47 81.34 MB
/dev/sda4 6 Fri Apr 12 04:30:02 2019 +0100 /dumpx/DUMP4X/var/level6/
+55 86.53 MB
/dev/sdb1 6 Fri Apr 12 04:31:47 2019 +0100 /dumpx/DUMP4X/var/level6/
+56 27.73 MB
/dev/sdb2 6 Fri Apr 12 04:33:33 2019 +0100 /dumpx/DUMP4X/var/level7/
+58 57.32 MB
__EOD1__
while ( <$file1FH> )
{
print unless m{$rxExcl};
}
close $file1FH or die $!;'
/dev/sda3 6 Fri Apr 12 04:27:19 2019 +0100 /dumpx/DUMP3X/var/level6/
+47 81.34 MB
/dev/sdb1 6 Fri Apr 12 04:31:47 2019 +0100 /dumpx/DUMP4X/var/level6/
+56 27.73 MB
I hope this is useful.