my $match = pack 'H*', '53005f00560045005200530049004f004e005f004' . '9004e0046004f0000000000bd04effe00000100'; open(FILE,$file) or die $!; while () { if (/$match(\S{2})(\S{2})(\S{2})(\S{2})/) { print "Found match!"; print join('.',map {unpack 'H*',$_; } ($1,$2,$3,$4); } } close(FILE);