In /usr/bin/check-enhancements line 61:
    PACKAGEFILES=$(apt-get indextargets --format '$(FILENAME)' "Created-By: Packages")
                                                 ^-----------^ SC2016: Expressions don't expand in single quotes, use double quotes for that.


In /usr/bin/check-enhancements line 63:
    EN=$(/usr/lib/apt/apt-helper cat-file $PACKAGEFILES | grep-dctrl -n -s Package -F Enhances -X "${1}")
                                          ^-----------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
    EN=$(/usr/lib/apt/apt-helper cat-file "$PACKAGEFILES" | grep-dctrl -n -s Package -F Enhances -X "${1}")


In /usr/bin/check-enhancements line 73:
    for e in `echo "${EN}" | sort | uniq | xargs` # now sort and unify
             ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
    for e in $(echo "${EN}" | sort | uniq | xargs) # now sort and unify


In /usr/bin/check-enhancements line 79:
	       0) OUT=`apt-cache policy ${e} | head -3 | paste -s | grep "Installed: (none)"`
                      ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.
                                        ^--^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
	       0) OUT=$(apt-cache policy "${e}" | head -3 | paste -s | grep "Installed: (none)")


In /usr/bin/check-enhancements line 81:
	       1) OUT=`apt-cache policy ${e} | head -3 | paste -s`
                      ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.
                                        ^--^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
	       1) OUT=$(apt-cache policy "${e}" | head -3 | paste -s)


In /usr/bin/check-enhancements line 90:
for op in $@
          ^-- SC2068: Double quote array expansions to avoid re-splitting elements.


In /usr/bin/check-enhancements line 123:
      PKGS+=(${op})
             ^---^ SC2206: Quote to prevent word splitting/globbing, or split robustly with mapfile or read -a.


In /usr/bin/check-enhancements line 134:
    pkgs_enhancing_pkg_status $cmdline_pkg
                              ^----------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
    pkgs_enhancing_pkg_status "$cmdline_pkg"


In /usr/bin/check-enhancements line 142:
       pkgs_enhancing_pkg_status $installed
                                 ^--------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
       pkgs_enhancing_pkg_status "$installed"

For more information:
  https://www.shellcheck.net/wiki/SC2068 -- Double quote array expansions to ...
  https://www.shellcheck.net/wiki/SC2206 -- Quote to prevent word splitting/g...
  https://www.shellcheck.net/wiki/SC2016 -- Expressions don't expand in singl...