cperl-electric-keywords is a variable defined in `cperl-mode.el'.
Its value is

*Not-nil (and non-null) means keywords are electric in CPerl.
Can be overwritten by `cperl-hairy' if nil.

Uses `abbrev-mode' to do the expansion. If you want to use your
own abbrevs in cperl-mode, but do not want keywords to be
electric, you must redefine `cperl-mode-abbrev-table': do
M-x edit-abbrevs, search for `cperl-mode-abbrev-table', and, in
that paragraph, delete the words that appear at the ends of lines and
that begin with "cperl-electric".

You can customize this variable.