Conditional statements are performed using if statements:

if g:animal_kind == 'cat'
  echo g:animal_name . ' is a cat'
elseif g:animal_kind == 'dog'
  echo g:animal_name . ' is a dog'
else
  echo g:animal_name . ' is something else'
endif

You can also make this operation inline:

echo g:animal_name . (g:is_cat ? 'in'is a cat' : 'in'is something else')

Vim supports all of the logical operators you're used to from other languages:

• && - and
• || - or
• ! - not

For example, you can do this:

if !(g:is_cat || g:is_dog)
  echo g:animal_name . ' is something else'
endif

In the previous example, you'll get to g:animal_name . ' is something else' only if neither g:is_cat or g:is_dog are true.

This can also be written with the && operator:

if !g:is_cat && !g:is_dog
  echo g:animal_name . ' is something else'
endif

Since text editing implies operating on strings, Vim has additional text-specific comparison operators:

• == compares two string; case sensitivity depends on user's settings (see later)
• ==? explicitly case insensitive comparison
• ==# explicitly case sensitive comparison
• =~ checks a match against an expression on the right (=~? or =~# to make those explicitly case insensitive or sensitive)
• !~ checks that a string does not match an expression on the right (=~#or !~# to make those explicitly case insensitive or sensitive)

The default behavior of ==, as well as =~ and !~ (case sensitive or case insensitive) depends on the ignorecase setting.

Here are some examples:

'cat' ==? 'CAT'                     " true
'cat' ==# 'CAT'                     " false
set ignorecase | 'cat' == 'CAT'     " true
'cat' =~ 'c.+'                     " true
'cat' =~# 'C.+'                    " false
'cat' !~ '.at'                      " false
'cat' !~? 'C.+'                    " false