Question

I have a simple Perl script that prints out @INC as the following:

#!/usr/bin/perl
print $_, "\n" for @INC;

I execute the script in 2 different ways with ./test.pl and perl test.pl, the output as the following:

[neevek@~/bin]$ ./test.pl 
/Library/Perl/5.12/darwin-thread-multi-2level
/Library/Perl/5.12
/Network/Library/Perl/5.12/darwin-thread-multi-2level
/Network/Library/Perl/5.12
/Library/Perl/Updates/5.12.3
/System/Library/Perl/5.12/darwin-thread-multi-2level
/System/Library/Perl/5.12
/System/Library/Perl/Extras/5.12/darwin-thread-multi-2level
/System/Library/Perl/Extras/5.12
.   
[neevek@~/bin]$ perl test.pl 
/opt/local/lib/perl5/site_perl/5.12.3/darwin-multi-2level
/opt/local/lib/perl5/site_perl/5.12.3
/opt/local/lib/perl5/vendor_perl/5.12.3/darwin-multi-2level
/opt/local/lib/perl5/vendor_perl/5.12.3
/opt/local/lib/perl5/5.12.3/darwin-multi-2level
/opt/local/lib/perl5/5.12.3
/opt/local/lib/perl5/site_perl
/opt/local/lib/perl5/vendor_perl
.   

My question is: what’s behind the scenes for executing a perl script with ./script.pl and perl script.pl? what causes the script to output different @INC?

Answer 1

The script is executing perl from /usr/bin through the shebang line, but launching the script from the command line uses a different perl binary, from /opt/somewhere (see which perl for the path). You can use #!/usr/bin/env perl to make both options behave the same.