Actually you could call a wrapper-shell-script which sources and calls a second perl-script.

The perl-script use Data::Dumper to serialize %ENV and prints the string to STDOUT.

opening the shell script with "wrapper.sh |" should¹ be sufficent to grab the dump.

the second perl-script might look overhead but it's cleaner and you don't need to worry about k/ba/c-sh compatibilities and about JSON.

¹) open

               and if the filename
               ends with a '|', the filename is interpreted as a comma
+nd which
               pipes output to us. 
[download]

               For three or more arguments if MODE is '|-', the filena
+me is
               interpreted as a command to which output is to be piped
+, and if
               MODE is '-|', the filename is interpreted as a command 
+which
               pipes output to us.
[download]