$ cat -n tt
     1  #!/usr/bin/perl
     2
     3  my $perl = <<'EOF';
     4  sub {
     5  my $x = 123;
     6  $x += shift;
     7  print "x is $x\n"
     8  }
     9  EOF
    10
    11  my $cf = eval $perl;
    12
    13  $cf->(4);

$ perl -d tt

Loading DB routines from perl5db.pl version 1.28
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(tt:3):   my $perl = <<'EOF';
main::(tt:4):   sub {
main::(tt:5):   my $x = 123;
main::(tt:6):   $x += shift;
main::(tt:7):   print "x is $x\n"

DB<8> s
main::(tt:11):  my $cf = eval $perl;

DB<8> s
main::((eval 20)[tt:11]:7):     ;