dpkg-parsechangelog | grep Ver | perl -ne '/\s(.*?)\-/ ; print $1'

but it's better to use:

version := $(shell dpkg-parsechangelog | grep ^Version: \
                | cut -d' ' -f2 | cut -d- -f1)

(this latter is for debian/rules)

or even better:

version := $(shell dpkg-parsechangelog --show-field=Version | cut -d- -f1)