Summary and Info:

Given the following two packages:

1st build-support/pango-perl-nocheck:

Provides : pango-perl=1.227
Conflicts With : pango-perl
Replaces : pango-perl
Depends On : pango glib-perl cairo-perl perl>=5.26 perl<5.27
...

2nd extra/pango-perl:

Name : pango-perl
Version : 1.227-2
Depends On : pango glib-perl cairo-perl perl>=5.24 perl<5.25
...

and the following pacman.conf:

...

[build-support]
Include = /etc/pacman.d/mirrorlist

[extra]
Include = /etc/pacman.d/mirrorlist

...

and both repositories, "build-support" and "extra", are on a mirror in the mirrorlist (https://mirror.archlinux32.org/$arch/$repo), I have the following:

> pacman -Ss pango-perl
build-support/pango-perl-nocheck 1.227-4
Perl bindings for Pango -- without check()
extra/pango-perl 1.227-2
Perl bindings for Pango

as expected, but
> pacman -S pango-perl
warning: cannot resolve "perl<5.25", a dependency of "pango-perl"
:: The following package cannot be upgraded due to unresolvable dependencies:
pango-perl

:: Do you want to skip the above package for this upgrade? [y/N]

So it tries to install pango-perl from extra instead of pango-perl-nocheck, providing pango-perl, from build-support.

Steps to Reproduce:
Put mirror.archlinux32.org into mirrorlist (on an i686 system), add repository build-support to pacman.conf above extra, do "pacman -Sy pango-perl".

Although this description is for i686 only, I don't think the issue is specific to i686.

If this is intended behaviour, what is the supposed way of replacing one package by another one with different name (due to (slightly) different content)?

Cheers, deep42thought