split is happy with any string (or anything that can be converted to a string) as a /PATTERN/, e.g.,

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my $tim = '10:00:10.004';
 ;;
 my @outputlist = split '[:.]', $tim;
 dd \@outputlist;
 ;;
 my $p = 10;
 @outputlist = split $p, $tim;
 dd \@outputlist;
"
[10, "00", 10, "004"]

["", ":00:", ".004"]
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However, I would incline to use  // qr// m// for any but the most simple and straightforward patterns; I vaguely recall pitfalls involving backslashes.