In /usr/bin/xzless line 46:
	LESSMETACHARS="$space$tab$nl'"';*?"()<>[|&^`#\$%=~'
                                    ^-- SC2089: Quotes/backslashes will be treated literally. Rewrite using set/"$@" or functions.


In /usr/bin/xzless line 49:
if test "$(less -V | { read less ver re && echo ${ver}; })" -ge 429; then
                       ^--^ SC2162: read without -r will mangle backslashes.
                            ^--^ SC2034: less appears unused. Verify use (or export if used externally).
                                     ^-- SC2034: re appears unused. Verify use (or export if used externally).
                                                ^----^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
if test "$(less -V | { read less ver re && echo "${ver}"; })" -ge 429; then


In /usr/bin/xzless line 56:
export LESSMETACHARS LESSOPEN
       ^-----------^ SC2090: Quotes/backslashes in this variable will not be respected.

For more information:
  https://www.shellcheck.net/wiki/SC2034 -- less appears unused. Verify use (...
  https://www.shellcheck.net/wiki/SC2089 -- Quotes/backslashes will be treate...
  https://www.shellcheck.net/wiki/SC2090 -- Quotes/backslashes in this variab...