Syntax for wildcard selection

This question just came up from a user use to our Informix application.  They
tried to do a wildcard search, thus "where field_name LIKE 'AB%VN'".  The
trailing values (after the %) are not recognized correctly.  With Informix
4GL, we wrote "where field_name MATCHES 'AB*VN'".  This finds any combination
of values with 'AB' as the first two characters, and 'VN' as the last two,
with any number of characters in between - including blanks.  How is this
accomplished with PostgreSQL?  Are we limited to wildcard searches as "where
field_name LIKE 'AB%'"?