#!/bin/sh
a=" after"
b="before "
m=" middle "
x=' a b '
y=' echo d '
unset v1 v2
# Note that the expandsion of $y and $x in the next statement are not quoted.
v1="before"$y" "$x"after"
printf '"v1":X%sX\n' "$v1"
printf 'v1:X%sX\n' $v1

# Note that the strings to which $y and $x are substituted here, but not as
# variable expansions.  Here "echo" becomes a command to execute with v2 set as
# a variable in the environment of the echo command, but it is not set in the
# current shell execution environment.
v2="before" echo d " " a b "after"
printf '"v2":X%sX\n' "$v2"
printf 'v2:X%sX\n' $v2

# Now see how those same sets of strings are handled when passed as arguments to
# a utility instead of being assigned to a variable...
printf 'v1string:X%sX\n' "before"$y" "$x"after"
printf 'v2string:X%sX\n' "before" echo d " " a b "after"

# Spaces still matter when variable expansions are separated by IFS characters.
set -xv
w=$b $m $a
z=$b$m$a
set +xv
# And, of course leading and trailing spaces disappear when fields are separated
# in unquoted arguments.
printf 'space between:X%sX\n' $b $m $a
printf 'no space between:X%sX\n' $b$m$a

"v1":Xbefore echo d   a b afterX
v1:XbeforeX
v1:XechoX
v1:XdX
v1:XaX
v1:XbX
v1:XafterX
d   a b after
"v2":XX
v2:XX
v1string:XbeforeX
v1string:XechoX
v1string:XdX
v1string:X X
v1string:XaX
v1string:XbX
v1string:XafterX
v2string:XbeforeX
v2string:XechoX
v2string:XdX
v2string:X X
v2string:XaX
v2string:XbX
v2string:XafterX
w=$b $m $a
+ w='before '
+ middle after
tester: line 28: middle: command not found
z=$b$m$a
+ z='before  middle  after'
set +xv
+ set +xv
space between:XbeforeX
space between:XmiddleX
space between:XafterX
no space between:XbeforeX
no space between:XmiddleX
no space between:XafterX

txts="\x1B[0m"$y" "$x"This is bizarre, why the inverted commas error?"

txts="\x1B[0m$y ${x}This is bizarre, why the inverted commas error?"

txts='\x1B[0m'"$y $x"'This is bizarre, why the inverted commas error?'