Shell Programming and Scripting

I have made a simple script to find all programs that use a tcp wrapper, it will supply a reasonable default for my system if none is given.

After some digging I realized that the expansion operators pass their default return value single quoted (according to bash -x trace). I have wildcard expansions in my return value, and it works if used with eval.

Its working perfect with eval, but I don't know why.

Code:

#! /bin/bash

ldd_path="$*"

while read line
do
     if [[ "$line" =~ ^/.*:$ ]]
     then
          current_binary="$line"
     elif [[ "$line" =~ .*libwrap.so.0.* ]]
     then
          printf '%s\n' "$current_binary"
     fi
done < <(eval ldd ${ldd_path:-"/usr/bin/* /usr/sbin/*"})

My question is really how is eval working with wildcards if they are passed with single quotes, bash -x shows eval working on this:

Code:

eval ldd '/usr/bin/* /usr/sbin/*'

I though evaluation order will prevent this from working but it is.

Can somebody elaborate on this for me