Basic HTML version of Foils prepared Sept 20 97

Foil 47 (?..) Constructs in Regular Expressions -III

From Perl5 and Advanced Perl4 Features Computational Science for Information Age Course CPS616 -- Sept 20 97. by Geoffrey C. Fox,Nancy McCracken,Tom Scavo
1 (?:regexp) means a simple grouping of regexp as a unit -- equivalent to (regexp) except it does not generate a $n reference
2 regexp1(?=regexp2) matches to regexp1 followed by regexp2 but regexp2 is not considered part of match
  • i.e. regexp1 in $MATCH, regexp2 in $POSTMATCH
3 regexp1(?!regexp2) matches to regexp1 NOT followed by regexp2
4 (?i) (?m) (?imsx) etc are equivalent to specifying modifiers i, m or i and m and s and x respectively
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