perl -e 'my $mac = "10:27:be:0F:db:04"; $mac =~ tr/[[:xdigit:]]//cd; print "$mac\n";'  
::::d:

perl -e 'my $mac = "10:27:be:0F:db:04"; $mac =~ tr/[^[:xdigit:]]//cd; print "$mac\n";'  
::::d:

perl -e 'my $mac = "10:27:be:0F:db:04"; $mac =~ tr/[0-9a-fA-F]//cd; print "$mac\n";'  
1027be0Fdb04