Further inspection of the problem leads me to the conclusion that this may not be related to encode. I fired up my Debugger and performed some tests. Notice how the Character \N{greek:alpha} was found on Linux, but not on AIX:
AIX 7.2:
DB<1> use charnames qw(greek)
DB<2> print "\N{alpha}"
Use of uninitialized value $txt in pattern match (m//) at /usr/opt/per
+l5/lib/5.20.1/_charnames.pm line 459.
[...]
Unknown charname 'alpha' at (eval 9)[/usr/opt/perl5/lib/5.20.1/perl5db
+.pl:732] line 2, within string
DB<3> print "\N{U+03B1}"
Wide character in print at (eval 10)[/usr/opt/perl5/lib/5.20.1/perl5db
+.pl:732] line 2.
[...]
α
DB<4> print "\N{greek:alpha}"
Use of uninitialized value $txt in pattern match (m//) at /usr/opt/per
+l5/lib/5.20.1/_charnames.pm line 459.
[...]
Unknown charname 'greek:alpha' at (eval 11)[/usr/opt/perl5/lib/5.20.1/
+perl5db.pl:732] line 2, within string
Ubuntu 14.04
DB<1> use charnames qw(greek)
DB<2> print "\N{alpha}"
Unknown charname 'alpha' at (eval 8)[/usr/share/perl/5.18/perl5db.pl:
+732] line 2, within string
DB<3> print "\N{U+03B1}"
Wide character in print at (eval 9)[/usr/share/perl/5.18/perl5db.pl:7
+32] line 2.
α
DB<4> print "\N{greek:alpha}"
Wide character in print at (eval 10)[/usr/share/perl/5.18/perl5db.pl:
+732] line 2.
α
Guess there is something messed up with the AIX character-table? | 