VS Code snippet transform: convert camel case to Pascal case or vice versa

gistfile1.txt

// If you want to convert a PascalCase variable to camelCase, you can do the following:
// Where `n` is the tab stop you want to reference
${n/^(.)(.*)$/${1:/downcase}${2}/}

// Example: ${1:This is my original} => ${1/^(.)(.*)$/${1:/downcase}${2}/}


// If you want to convert a camelCase variable to PascalCase, you can do the following:
// Where `n` is the tab stop you want to reference
${n/^(.)(.*)$/${1:/upcase}${2}/}

// Example: ${1:This is my original} => ${1/^(.)(.*)$/${1:/upcase}${2}/}

Seems like there is /camelcase and /pascalcase transform, which could make everything simpler.
But this acts like it's meant to convert snake_case to camelCase, not PascalCase to camelCase.
There is also /capitalize transform, which can be used for converting camelCase to PascalCase, but there is no opposite transform.

Therefore these do give expected result,

${1:snake_to_camel} => ${1/(.*)/${1:/camelcase}/} // result is "snakeToCamel"
${2:snake_to_pascal} => ${2/(.*)/${1:/pascalcase}/} // result is "SnakeToPascal"
${3:camelToPascal} => ${3/(.*)/${1:/capitalize}/} // result is "CamelToPascal"

But these do not give expected result.

${1:PascalToCamel} => ${1/(.*)/${1:/camelcase}/} // result is "pascaltocamel"
${2:camelToPascal} => ${2/(.*)/${1:/pascalcase}/} // result is "Cameltopascal"

What a mess.

thank you

Answer to vscode snippet transform file name in the snippet to camel case or pascal case variable

given file_name_foo.ext file

${TM_FILENAME_BASE/^(.*)_foo$/${1:/pascalcase}/}  ==> FileName
${TM_FILENAME_BASE/^(.*)_foo$/${1}/}  ==> file_name
${TM_FILENAME_BASE/^(.*)_foo$/${1:/upcase}/}  ==> FILE_NAME

:/camelcase works as well.