Substrings by Regular Expression

Hello-

The 7.2 version distributed with RedHat 8.0 seems not
to work for substrings and POSIX regular expressions.

I think this should work....

pds=>  select substring( str1 from ',' ) from address;
ERROR:  pg_atoi: error in ",": can't parse ","

Am I missing something?

TIA
J. Drummey
drumeng@yahoo.com