Perl, Why is @INC different?

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?

Creepie

Different perl binaries? What does which perl say? – Cog

which perl says /opt/local/bin/perl, but I used /usr/bin/perl for the shabang. you all are correct, thank you...but I could I have missed that... – Creepie

Unix lesson #1 (that I give to all newbies in the team). NEVER EVER EVER rely on current directory or PATH. ALWAYS use explicit fully qualified path. – Bezique

I’d say that relying on environment makes sense at least in some cases, for example it makes it easy to switch Perls with Perlbrew. – Microphone

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.

Microphone

Answer 2

You have two perl installations on your system.

When you execute ./test.pl, it's /usr/bin/perl that is chosen, as written on the first line of your script.

When you execute perl test.pl, it's the first perl found in the PATH environment variable that is chosen. Type which perl to discover where it is.

Consumable