st: how to extract numeric part of a string

["Plummer, Dale" <Dale.Plummer@Vanderbilt.edu>]

If I have a string variable, is there a way to extract out only the
number component?

Examples:

Var_source        Var_target
Abc123             123
Dog34              34
1209               1209
cat                 .

Thanks for any ideas.

Dale Plummer
Department of Preventive Medicine
Vanderbilt School of Medicine
A1124 MCN
Nashville, Tennessee 37232-2637
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