Was there an attempt to make reusable regular expressions?
Lex, the lexical analyser generator, supports this notation. In the "definitions" section, you can define patterns which you can then use in the "rules" section:

DIGIT    [0-9]

%%

{DIGIT}+"."{DIGIT}*  { return T_FNUM; }


Most lexer generators have something similar; ANTLR has "fragments", for example.