Here is an approach using split and avoiding a substitution:

>perl -wMstrict -le
"my $var= 'sclerosing 1954, 5-7, 54, 59f-60d, 90, 114';
 my (undef, $tail) = split m{\s* , \s*}xms, $var, 2;
 my $tag = qq{<t> $tail </t>};
 print $tag;
"
<t> 5-7, 54, 59f-60d, 90, 114 </t>
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If you feel you must use a regex substitution, read perlre as suggested by Perlbotics, and also perlretut and perlrequick, and take a look at the regex tutorials on this site: Pattern Matching, Regular Expressions, and Parsing.