First of all, refer to regexp(5) for the definitions of basic and extended
regular expressions.

From the command-line
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The following commands support basic regular expression matching:

  o grep(1)
  o sed(1)
  o ed(1)
  o ex(1)
  o vi(1)

The following commands support extended regular expression matching:

  o egrep(1) (grep -E)
  o awk(1)

Perl supports Perl regular expressions, a superset of extended regular
expressions.

Programmatically
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Use regcomp(3C).  Do not use regcmp(3X) or re_comp(3X); these are
obsolescent and may be removed in a future HP-UX release.