Returns the offset of where the lastm//g search left off for the variable in question ($_ is used when the variable is not specified). This offset is in characters unless the (no-longer-recommended)use bytes pragma is in effect, in which case the offset is in bytes. Note that 0 is a valid match offset.undef indicates that the search position is reset (usually due to match failure, but can also be because no match has yet been run on the scalar).
pos directly accesses the location used by the regexp engine to store the offset, so assigning topos will change that offset, and so will also influence the\G zero-width assertion in regular expressions. Both of these effects take place for the next match, so you can't affect the position withpos during the current match, such as in(?{pos() = 5}) ors//pos() = 5/e.
Settingpos also resets thematched with zero-length flag, described under"Repeated Patterns Matching a Zero-length Substring" in perlre.
Because a failedm//gc match doesn't reset the offset, the return frompos won't change either in this case. Seeperlre andperlop.
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