#...
 # alt1: match only, leave $var unmodified:
 my $var = "sclerosing 1954, 5–7, 54, 59f-60d, 90, 114";
 if ( $var =~ /^[^,]+,\s*(.+?)\s*$/ ) {
     print "Match: ==>$1<==\n"; 
     #  ==>5–7, 54, 59f-60d, 90, 114<==
 }
 
 # alt2: add <t>markup</t>, substitute $var2:
 my $var2 = "sclerosing 1954, 5–7, 54, 59f-60d, 90, 114";
 if ( $var2 =~ s{^([^,]+,\s*)(.+?)(\s*)$}{$1<t>$2</t>$3} ) {
     print "Markup: ==>$var2<==\n"; 
     # ==>sclerosing 1954, <t>5–7, 54, 59f-60d, 90, 114</t><==
 }
 #...